fix(openid): allow expires_in param to be null

Scripts/mysql-utf8mb4.sql

@@ -170,7 +170,7 @@ CREATE TABLE sogo_opend_id (
 	c_old_session              varchar(4096) DEFAULT '',
 	c_session_started           int(11)       NOT NULL,
 	c_refresh_token             varchar(4096) DEFAULT '',
-	c_access_token_expires_in    int(11)       NOT NULL,
+	c_access_token_expires_in    int(11)       DEFAULT '',
 	c_refresh_token_expires_in  int(11)       DEFAULT NULL,
 	PRIMARY KEY (c_user_session)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 ROW_FORMAT=DYNAMIC;